1. Field of the Invention
The present invention relates to a ceramic-metal composite joint body.
2. Related Art Statement
Referring to FIG. 1, such a ceramic-metal composite joint body has a construction such that a projection 2 of a ceramic member 1 is inserted into a recess 4 of a metal member 3 by means of known connection methods such as pressure insertion, thermal insertion, chill insertion or combination methods between such connection methods and soldering.
In the ceramic-metal composite joint body mentioned above, dimensions such as shaft diameter, surface roughness, etc. of the projection 2 of the ceramic member 1 are controlled into a common difference with respect to standard values. However, a circularity of the projection 2 is not controlled.
Therefore, in the ceramic-metal composite joint body mentioned above, an excessive stress concentration occurs at a connection edge between the projection 2 of the ceramic member 1 and the recess 4 of the metal member 3 due to the shape of the projection 2 especially the circularity of an outer portion of the projection 2. As a result, breakage of the projection 2 might be generated.
In the case of a connection between a metal member and a metal member, the circularity is not a problem because the metal members exhibit elastic deformation. However, in the case of the connection between a ceramic member and a metal member as shown in FIG. 1, if the circularity of the projection 2 of the ceramic member 1 is bad, prior to the elastic deformation of the recess 4 of the metal member 3 an excessive stress concentration is applied to the projection 2 of the ceramic member 1 which does not exhibit an elastic deformation, and the crack is generated in the projection 2.